Method and apparatus for controlling an actuatable safety device

ABSTRACT

A method for determining a crash condition of a vehicle comprises the step of sensing crash acceleration in a first direction substantially parallel to a front-to-rear axis of the vehicle and providing a first acceleration signal indicative thereof. The method also comprises the step of sensing crash acceleration in a second direction substantially parallel to a side-to-side axis of the vehicle and near opposite sides of the vehicle and providing second acceleration signals indicative thereof. The method further comprises the steps of determining a transverse crash value functionally related to the second acceleration signals and comparing the determined transverse crash value against a safing threshold. The method still further comprises the step of determining a crash condition of the vehicle in response to (a) the comparison and (b) the first acceleration signal.

FIELD OF THE INVENTION

The present invention relates to a method and apparatus for determininga vehicle crash condition and, in particular, to a method and apparatusfor controlling an actuatable vehicle safety device in response todetermining the occurrence of a vehicle crash condition.

BACKGROUND OF THE INVENTION

Actuatable occupant restraint systems are used to help protect occupantsof a vehicle in a vehicle crash event. Such actuatable occupantrestraint systems may include an inflatable occupant restraint device,such as an air bag, to help protect a vehicle occupant upon thedetermined occurrence of a vehicle crash event.

U.S. Pat. No. 5,935,182 to Foo et al., assigned to TRW Inc., discloses amethod and apparatus for determining such crash events and isparticularly directed to discriminating a vehicle crash condition usingvirtual crash sensing. U.S. Pat. No. 6,036,225 to Foo et al., assignedto TRW Inc., discloses a method and apparatus for controlling amultistage actuatable restraining system in a vehicle using crashseverity index values. U.S. Pat. No. 6,186,539 to Foo et al., alsoassigned to TRW Inc., discloses a method and apparatus for controlling amultistage actuatable restraining device using crash severity indexingand crush zone sensors. U.S. Patent Application Publication No.2007/0005207 to Foo et al., assigned to TRW Automotive U.S. LLC,discloses a method and apparatus for controlling an actuatablerestraining device using side satellite accelerometers.

SUMMARY OF THE INVENTION

The present invention is directed to a method and apparatus fordetermining a vehicle crash condition and, in particular, to a methodand apparatus for controlling an actuatable vehicle safety device inresponse to determining the occurrence of a vehicle crash condition.

In accordance with an example embodiment of the present invention, amethod for determining a crash condition of a vehicle comprises the stepof sensing crash acceleration in a first direction substantiallyparallel to a front-to-rear axis of the vehicle and providing a firstacceleration signal indicative thereof. The method also comprises thestep of sensing crash acceleration in a second direction substantiallyparallel to a side-to-side axis of the vehicle and near opposite sidesof the vehicle and providing second acceleration signals indicativethereof. The method further comprises the steps of determining atransverse crash value functionally related to the second accelerationsignals and comparing the determined transverse crash value against asafing threshold. The method still further comprises the step ofdetermining a crash condition of the vehicle in response to (a) thecomparison and (b) the first acceleration signal.

In accordance with another example embodiment of the present invention,an apparatus for determining a crash condition of a vehicle comprises afirst accelerometer for sensing crash acceleration in a first directionsubstantially parallel to a front-to-rear axis of the vehicle andproviding a first acceleration signal indicative thereof. The apparatusalso comprises second accelerometers for sensing crash acceleration in asecond direction substantially parallel to a side-to-side axis of thevehicle and near opposite sides of the vehicle and providing secondacceleration signals indicative thereof. The apparatus further comprisesa controller for determining a transverse crash value functionallyrelated to the second acceleration signals and comparing the transversecrash value against a safing threshold. The controller also determines acrash condition of the vehicle in response to (a) the comparison and (b)the first acceleration signal.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features and advantages of the present inventionwill become apparent to one skilled in the art upon consideration of thefollowing description of the invention and the accompanying drawings, inwhich:

FIG. 1 is a schematic top view of a vehicle having an actuatableoccupant restraint system in accordance with an example embodiment ofthe present invention;

FIG. 2 is a functional block diagram of the control portion of theapparatus of FIG. 1;

FIG. 3 is a functional block diagram showing a first part of a controlprocess used by the control portion of FIG. 2 in accordance with oneexample embodiment of the present invention;

FIG. 4 is a functional block diagram showing a second part of thecontrol process shown in FIG. 3; and

FIG. 5 is a functional block diagram showing part of a control processused by the control portion of FIG. 2 in accordance with a secondexample embodiment of the present invention.

DETAILED DESCRIPTION

Referring to FIGS. 1 and 2, an apparatus 10 is mounted in a vehicle 12for determining a crash condition of the vehicle and controllingactuation of an actuatable occupant restraint system 14, in accordancewith an example of the present invention. The actuatable occupantrestraint system 14 comprises, for example, a first frontal inflatableoccupant restraint device 16, such as a steering wheel-mounted air bagmodule, located on a driver side 18 of the vehicle 12. The actuatableoccupant restraint system 14 may also comprise a second frontalinflatable occupant restraint device 20, such as an instrumentpanel-mounted air bag module, located on a passenger side 22 of thevehicle 12.

The actuatable occupant restraint system 14 may further comprise a firstside impact inflatable occupant restraint device 24, such as adoor-mounted air bag module, a seat-mounted air bag module, or a roofrail-mounted curtain air bag module, located on the driver side 18 ofthe vehicle 12. The first side impact inflatable occupant restraintdevice 24 may alternatively be located anywhere in or adjacent to sidestructure of the vehicle 12, such as the side pillars and/or side bodypanels. The actuatable occupant restraint system 14 may still furthercomprise a second side impact inflatable occupant restraint device 26,such as a door-mounted air bag module, a seat-mounted air bag module, ora roof rail-mounted curtain air bag module, located in or adjacent toside structure on the passenger side 22 of the vehicle 12. Theactuatable occupant restraint system 14 may yet further or alternativelycomprise an actuatable seat belt occupant restraint device, such as adriver side seat belt pretensioner 28 and/or a passenger side seat beltpretensioner 29. The actuatable occupant restraint system 14 mayadditionally or alternatively comprise any actuatable occupant restraintdevice that helps to protect a vehicle occupant in response to an impactto the vehicle 12.

The occupant restraint devices 16, 20, 24, 26, 28 and 29 of theactuatable occupant restraint system 14 are actuatable restraint orsafety devices of the vehicle 12. Other actuatable restraint or safetydevices of the vehicle 12 that may be actuated in response to an impactto or a crash condition of the vehicle include vehicle door locks (notshown) and may include a suspension control system (not shown), adeployable roll bar (not shown), and an external air bag (not shown) orother inflatable devices internal or external to the vehicle.

The apparatus 10 further comprises a collision or crash sensor assembly30 located at a substantially central location in the vehicle 12. Thesensor assembly 30 includes a first crash acceleration sensor 32, suchas an accelerometer, having its axis of sensitivity oriented to sensecrash acceleration in a direction substantially parallel to alongitudinal or front-to-rear axis of the vehicle 12. The longitudinalor front-to-rear axis of the vehicle 12 is designated the X-axis inFIG. 1. The first crash acceleration sensor 32 provides a crashacceleration signal designated CCU_1X. The sensor assembly 30 alsocomprises a second crash acceleration sensor 34, such as anaccelerometer, having its axis of sensitivity oriented to sense crashacceleration in a direction substantially parallel to a transverse orside-to-side axis of the vehicle 12. The transverse or side-to-side axisof the vehicle 12 is designated the Y-axis in FIG. 1 and is orientedsubstantially perpendicular to the X-axis. The second crash accelerationsensor 34 provides a crash acceleration signal designated CCU_1Y.

The first crash acceleration sensor 32, in accordance with one exampleembodiment of the present invention, has a nominal sensitivity of ±100g's (g being the value of acceleration due to earth's gravity, i.e., 32feet per second squared or 9.8 meters per second squared). The secondcrash acceleration sensor 34, in accordance with one example embodimentof the present invention, has a nominal sensitivity of ±20 g's.

The crash acceleration signals CCU_1X and CCU_1Y from the crashacceleration sensors 32 and 34, respectively, can take any of severalforms. Each of the crash acceleration signals CCU_1X and CCU_1Y can haveamplitude, frequency, pulse duration, and/or any other electricalcharacteristic that varies as a function of the sensed crashacceleration. In the example embodiment shown in FIGS. 1 and 2, thecrash acceleration signals CCU_1X and CCU_1Y have frequency andamplitude characteristics indicative of the sensed crash acceleration,i.e., that vary as a function of the sensed crash acceleration. Thus,each of the crash acceleration signals CCU_1X and CCU_1Y has anelectrical characteristic functionally related to the sensed crashacceleration along the axis of sensitivity of the corresponding crashacceleration sensor 32 or 34, respectively.

The apparatus 10 may also include two driver side satellite crashacceleration sensors 36 and 40 located in or adjacent or near to a sidestructure on the driver side 18 of the vehicle 12, such as in the driverside vehicle B-pillar 42 or in the driver side door 44. The sidesatellite crash acceleration sensor 36 has an axis of sensitivityoriented to sense crash acceleration in a direction substantiallyparallel to the vehicle's Y-axis and provides a signal designatedRAS_1BY. The side satellite crash acceleration sensor 40 has an axis ofsensitivity oriented to sense crash acceleration in a directionsubstantially parallel to the vehicle's X-axis and provides a signaldesignated RAS_1BX. Although the side satellite crash accelerationsensors 36 and 40 are described as being separate sensors, they may becombined in a single XY sensor.

The apparatus 10 may further include two passenger side satellite crashacceleration sensors 38 and 46 located in or adjacent or near to a sidestructure on the passenger side 22 of the vehicle 12, such as in thepassenger side B-pillar 48 or in the passenger side door 50. The sidesatellite crash acceleration sensor 38 has an axis of sensitivityoriented to sense crash acceleration in a direction substantiallyparallel to the vehicle's Y-axis and provides a signal designated asRAS_2BY. The side satellite crash acceleration sensor 46 has an axis ofsensitivity oriented to sense crash acceleration in a directionsubstantially parallel to the vehicle's X-axis and provides a signaldesignated as RAS_2BX. Although the side satellite crash accelerationsensors 38 and 46 are described as being separate sensors, they may becombined in a single XY sensor.

The crash acceleration signals RAS_1BY, RAS_1BX, RAS_2BY, and RAS_2BXfrom the side satellite crash acceleration sensors 36, 40, 38 and 46,respectively, can take any of several forms. Each of the crashacceleration signals RAS_1BY, RAS_1BX, RAS_2BY, and RAS_2BX can haveamplitude, frequency, pulse duration, and/or any other electricalcharacteristic that varies as a function of the sensed crashacceleration. In the embodiment of FIGS. 1 and 2, the crash accelerationsignals RAS_1BY and RAS_2BY have frequency and amplitude characteristicsthat vary as a function of the sensed crash acceleration in a directionsubstantially parallel to the vehicle's Y-axis. The crash accelerationsignals RAS_1BX and RAS_2BX have frequency and amplitude characteristicsthat vary as a function of the sensed crash acceleration in a directionsubstantially parallel to the vehicle's X-axis. Thus, each of the crashacceleration signals RAS_1BY, RAS_1BX, RAS_2BY, and RAS_2BX has anelectrical characteristic that varies as a function of the sensed crashacceleration along the axis of sensitivity of the corresponding sidesatellite crash acceleration sensor 36, 40, 38 or 46, respectively. Sidesatellite crash acceleration sensors 36 and 38 are arranged to senseacceleration and provide positive crash acceleration values in oppositedirections.

The apparatus 10 may include other Y-axis and X-axis side satellitecrash acceleration sensors. Such other Y-axis and X-axis side satellitecrash acceleration sensors may be mounted in or adjacent to C-pillars 52and 54 on the driver side 18 and passenger side 22, respectively, of thevehicle 12 and/or in or adjacent to D-pillars 56 and 58 on the driverside 18 and passenger side 22, respectively, of the vehicle. If C-pillarand/or D-pillar side satellite crash acceleration sensors are used,their signals would be designated as RAS_C3Y and RAS_C3X (driver sideC-pillar 52), RAS_C4Y and RAS_C4X (passenger side C-pillar 54), RAS_D5Yand RAS_D5X (driver-side D-pillar 56), and RAS_D6Y and RAS_D6X(passenger side D-pillar 58), respectively. In the embodiment of theinvention shown in FIGS. 1 and 2, however, only side satellite crashacceleration sensors 36, 40, 38 and 46 are present.

Referring to FIG. 2, the apparatus 10 further includes a controller 70.The crash acceleration signals CCU_1X and CCU_1Y from the crashacceleration sensors 32 and 34, respectively, and the crash accelerationsignals RAS_1BY and RAS_2BY from side satellite crash accelerationsensors 36 and 38, respectively, are provided to the controller 70. Inaccordance with one example embodiment of the present invention, thecontroller 70 may be a microcomputer programmed to execute a controlprocess, including one or more algorithms. The functions performed bythe controller 70 could, however, be carried out by other digital and/oranalog circuitry, including separate electrical or electroniccomponents, which could be assembled on one or more circuit boards usingdiscrete circuitry or fabricated as an application specific integratedcircuit (“ASIC”).

In accordance with an example embodiment of the present invention, thecontroller 70 monitors the crash acceleration signals CCU_1X and CCU_1Yfrom the crash acceleration sensors 32 and 34, respectively, and thecrash acceleration signals RAS_1BY and RAS_2BY from side satellite crashacceleration sensors 36 and 38, respectively. The controller 70 performsone or more crash determination algorithms to determine whether avehicle crash condition exists. If the controller 70 determines that avehicle crash event is occurring for which actuation or deployment ofthe actuatable occupant restraint system 14 or individual occupantrestraint devices or other actuatable safety devices of the vehicle isdesired, the devices will be actuated. The controller 70 has the abilityto discriminate between a deployment crash event and a non-deploymentcrash event.

The crash determination algorithms performed by the controller 70determine certain values from the crash acceleration signals CCU_1X,CCU_1Y, RAS_1BY, and RAS_2BY. The determined values are used indetermining whether a vehicle crash condition exists and whether theactuatable occupant restraint system 14 or individual occupant restraintdevices or any other actuatable safety device of the vehicle should bedeployed or actuated. If a determination is made, in accordance with thedetermined values, to deploy or actuate the actuatable occupantrestraint system 14 or individual occupant restraint devices, such asthe first frontal inflatable occupant restraint device 16 or the secondfrontal inflatable restraint device 20, or any other actuatable safetydevice of the vehicle, the controller 70 outputs an appropriatedeployment signal or command. Multi-stage devices may be actuated atdifferent times depending on the determined values and the time ofthreshold crossings or different devices may be actuated at differenttimes depending on the determined values and the times of thresholdcrossings.

The apparatus 10, in accordance with one example embodiment of theinvention, uses only the crash acceleration signals CCU_1X, CCU_1Y,RAS_1BY and RAS_2BY in determining whether a vehicle crash conditionexists and whether the actuatable occupant restraint system 14 orindividual actuatable occupant restraint or safety devices of thevehicle should be deployed or actuated. The apparatus 10 mayalternatively also employ the additional crash acceleration signalsRAS_1BX and RAS_2BX from additional side satellite crash accelerationsensors 40 and 46, with or without filtering, in crash determinationand/or deployment or actuation decisions. Other signals that may bereceived and employed in crash determination and/or deployment oractuation decisions, in addition to the crash acceleration signalsCCU_1X, CCU_1Y, RAS_1BY, and RAS_2BY, are signals RAS_C3Y, RAS_C3X,RAS_C4Y, RAS_C4X, RAS_D5Y, RAS_D5X, RAS_D6Y, and RAS_D6X from optionalC-pillar and/or D-pillar side satellite crash acceleration sensors if sodesired to aid in detecting a specific type of collision event. Stillother signals that may be received and employed in crash determinationand/or deployment or actuation decisions are signals from a driverand/or passenger seat belt buckle switch sensor that provides a signalindicating whether the buckle is latched or unlatched, a driver and/orpassenger weight sensor that provides a signal indicative of the seatoccupant's sensed weight, and sensors that provide signals indicative ofother vehicle occupant information, such as presence, position, height,girth, movement, and/or use of a child seat.

Referring to FIGS. 3 and 4, the controller 70 determines whether adeployment vehicle crash condition exists and controls the actuatableoccupant restraint system 14 using a control process and logic shown inaccordance with one example embodiment of the present invention. Theprocess and logic shown and described in FIGS. 3 and 4 is specificallydirected to controlling an actuatable occupant restraint device on thedriver side 18 of the vehicle 12, such as the first frontal inflatableoccupant restraint device 16. Nonetheless, this process and logic isrepresentative of the process and logic that may be used to control anyactuatable restraint of the vehicle 12, such as the second frontalinflatable occupant restraint device 20 on the passenger side 22 of thevehicle 12 or any other actuatable occupant restraint device that helpsto protect a vehicle occupant in response to a crash condition of thevehicle 12. The control process and logic may also be used to controlany actuatable safety device of the vehicle 12, such as vehicle doorlocks, a suspension control system, a deployable roll bar and/or anexternal air bag or other inflatable device external or internal to thevehicle.

In accordance with the example embodiment control process of FIGS. 3 and4, the crash acceleration sensor 32 provides an acceleration signalCCU_1X having a characteristic (e.g., frequency and amplitude)indicative of the vehicle's acceleration in a direction substantiallyparallel to the X-axis of the vehicle 12. The acceleration signal CCU_1Xis provided to a low-pass-filter (“LPF”) function 72 of the controller70. The LPF function 72 filters the acceleration signal CCU_1X toeliminate extraneous signal components, such as frequencies resultingfrom extraneous vehicle operating events and/or from road noise. Thesignal components removed through filtering are not useful indiscriminating whether a vehicle crash event is occurring and whether avehicle crash event is occurring for which deployment of a driver sideactuatable occupant restraint device, such as the first frontalinflatable occupant restraint device 16, is desired. Empirical testingor calculation may be used to determine the signal components useful fordiscrimination of a vehicle crash condition in a vehicle of interestand/or determining whether a vehicle crash event is occurring for whichdeployment of a driver side actuatable occupant restraint device isdesired. Signal components indicative of a vehicle crash conditionand/or useful in determining whether a vehicle crash event is occurringfor which deployment of a driver side actuatable occupant restraintdevice is desired are output for further processing.

The filtered output signal from the LPF function 72 is provided to ananalog-to-digital (“A/D”) converter function 74 of the controller 70.The A/D converter function 74 converts the filtered crash accelerationsignal into a digital signal. The output of the A/D converter function74 may be filtered with another filter function (not shown) havingfilter values determined for the purpose of eliminating small drifts andoffsets associated with the A/D conversion. This other filter functionmay be digitally implemented within the controller 70. A determinationand comparison function 76 of the controller 70 determines two crashmetric values, VEL_REL_1X and DISPL_REL_1X, from the filtered crashacceleration signal CCU_1X. Specifically, the determination andcomparison function 76 determines VEL_REL_1X, which is velocity in adirection substantially parallel to the X-axis, by integrating thefiltered crash acceleration signal CCU_1X. The determination andcomparison function 76 also determines DISP_REL_1X, which isdisplacement in a direction substantially parallel to the X-axis, bydouble integrating the filtered crash acceleration signal CCU_1X.

The crash displacement value and crash velocity value are preferablydetermined using a virtual crash sensing process fully described in U.S.Pat. No. 6,186,539 to Foo et al. and U.S. Pat. No. 6,036,225 to Foo etal. using a spring mass model of the occupant to account for springforces and damping forces. A detailed explanation of a spring-mass modelis found in U.S. Pat. No. 5,935,182 to Foo et al.

The determination and comparison function 76 of the controller 70compares the value VEL_REL_1X against at least one discriminationthreshold, which comparison is used to discriminate whether a crashevent is occurring. The discrimination threshold may be variable or maybe fixed. In accordance with one example embodiment of the invention,the determination and comparison function 76 compares the VEL_REL_1Xvalue as a function of the DISPL_REL_1X value against a first varyingdiscrimination, threshold 78 and a second varying discriminationthreshold 80. Graphical representations of the variations of the firstand second thresholds 78 and 80, in accordance with one exampleembodiment of the invention, are included in FIG. 3. As can be seen,after an initial high plateau followed by a large step or drop, thefirst and second thresholds 78 and 80 generally increase with increasingdisplacement DISPL_REL_1X in a direction substantially parallel to theX-axis. Empirical testing or calculation may be used to determine thevariation in the first and second thresholds 78 and 80 as a function ofthe displacement value DISPL_REL_1X needed to provide the desiredactuation control. The occurrence of the VEL_REL_1X value exceeding thefirst threshold 78 or the second threshold 80, as determined bydetermination and comparison function 76, is time latched by a latchfunction (not shown) of controller 70, which provides a digital HIGHsignal to an AND function 114 (FIG. 4) of the controller 70 for apredetermined time period. This portion of the example embodimentcontrol process is not shown in FIGS. 3 and 4, which instead illustratethe control process if the VEL_REL_1X value does not exceed either thefirst threshold 78 or the second threshold 80, as determined bydetermination and comparison function 76.

As part of comparing the VEL_REL_1X value as a function of theDISPL_REL_1X value against first and second varying thresholds 78 and80, the determination and comparison function 76 ensures that theVEL_REL_1X value lies outside of a safing immunity box 82 beforeinitiating any comparison. The purpose of the safing immunity box 82 isto filter misuse events and to prevent actuation of the occupantrestraint devices when crash velocity and/or crash displacement valuesare within the safing immunity box values. Misuse events include hammerblows, road bumps, door slams, and other events, which produce outputsignals from the crash acceleration sensor 32 that are not the result ofdeployment crash events. The safing immunity box 82 is represented byvalues of determined crash velocity and crash displacement below whichthe actuatable occupant restraint system 14 cannot be actuated. It isonly after the determined crash velocity VEL_REL_1X values and/or crashdisplacement DISPL_REL_1X values exceed the velocities and displacementsrepresented by the safing immunity box 82 and are, therefore, outside ofthe safing immunity box 82 that actuation of the actuatable occupantrestraint system 14 is normally permitted in response to crash metricdeterminations. Accordingly, the term “immunity” may, at times, be usedherein when discussing threshold, values that define whether or not anactuation of the actuatable occupant restraint system 14 is permitted.

The safing immunity box 82 defines an area bounded by predeterminedupper limit values of VEL_REL_1X and DISPL_REL_1X. When the determinedvalue of VEL_REL_1X is within the area of the safing immunity box 82,the safing function is OFF or at a digital LOW condition and, therefore,actuation of the actuatable occupant restraint system 14 cannot occur.If the value VEL_REL_1X is outside of the safing immunity box 82, thesafing function is ON or at a digital HIGH condition and, therefore, theactuatable occupant restraint system 14 can be actuated. In accordancewith the present invention, if the value VEL_REL_1X is outside thesafing immunity box 82 and then enters or re-enters the safing immunitybox, t the time period that the safing function is or remains ON isextended or enhanced after the value of VEL_REL_1X enters or reentersthe safing immunity box. This is referred to as a latched time period.Also, even though only one safing immunity box 82 is shown in FIG. 3,each threshold 78 and 80 may have an associated safing immunity box.

Although FIG. 3 shows a single output from determination and comparisonfunction 76, there are actually two outputs. A first output reflects theoccurrence of the VEL_REL_1X value exceeding the first threshold 78. Asecond output reflects the occurrence of the VEL_REL_1X value exceedingthe second threshold 80. The controller 70 distinguishes between thefirst and second outputs throughout the remaining steps of the controlprocess. The first output is used to control the actuation of onevehicle occupant restraint device or other vehicle safety device, suchas the first frontal inflatable occupant restraint device 16. The secondoutput is used to control the actuation of another vehicle occupantrestraint device or other vehicle safety device, such as a driver sideseat belt pretensioner 28. If only a single threshold is desired for allactuatable occupant restraint devices or other vehicle safety devices,only one of the thresholds 78 and 80 may be employed in the controlprocess of FIGS. 3 and 4. Similarly, if more than two thresholds aredesired to control more than two different occupant restraint devices orother safety devices in accordance with different thresholds, additionalthresholds may be employed in the control process of FIGS. 3 and 4.

Also in accordance with the example embodiment control process of FIGS.3 and 4, the crash acceleration sensor 34 provides an accelerationsignal CCU_1Y having a characteristic (e.g., frequency and amplitude)indicative of the vehicle's crash acceleration in a directionsubstantially parallel to the Y-axis of the vehicle 12 upon theoccurrence of a crash event. The acceleration signal CCU_1Y is providedto an LPF function 86 of the controller 70. The LPF function 86 filtersthe acceleration signal CCU_1Y to eliminate extraneous signalcomponents, such as frequencies resulting from extraneous vehicleoperating events and/or from road noise. The signal components removedthrough filtering are not useful in discriminating whether a vehiclecrash condition exists and whether a vehicle crash event is occurringfor which deployment of a driver side actuatable occupant restraintdevice, such as the first frontal inflatable occupant restraint device16, is desired. Empirical testing or calculation may be used todetermine the signal components useful for discrimination of a vehiclecrash condition in a vehicle of interest and/or determining whether avehicle crash event is occurring for which deployment of a driver sideactuatable occupant restraint device is desired. Signal componentsindicative of a vehicle crash condition and/or useful in determiningwhether a vehicle crash event is occurring for which deployment of adriver side actuatable occupant restraint device is desired are outputfor further processing.

The filtered output signal from the LPF function 86 is provided to anA/D converter function 88 of the controller 70. The AND converterfunction 88 converts the filtered crash acceleration signal CCU_1Y intoa digital signal. The output of the A/D converter function 88 may befiltered with another filter function (not shown) having filter valuesdetermined for the purpose of eliminating small drifts and offsetsassociated with the A/D conversion. This other filter function may bedigitally implemented within the controller 70. The filtered crashacceleration signal CCU_1Y is provided to a determination and comparisonfunction 90 of the controller 70, which determines a crash metric valueCCU_1YSigned_A_MA from the filtered crash acceleration signal CCU_1Y andalso determines a crash metric value CCU_1X_Long_A_MA from the filteredcrash acceleration signal CCU_1X.

The value CCU_1YSigned_A_MA is a moving average of acceleration assensed by the second crash acceleration sensor 34. This value isdetermined by calculating moving average-values of the associatedfiltered acceleration signal CCU_1Y from the second crash accelerationsensor 34. A moving average is the sum of the last predetermined numberof samples of the filtered acceleration signal divided by the number ofsamples. The average is updated by removing the oldest sample, replacingit with the latest sample, and then determining the new average. As theaverage value changes or “moves” over time, it is referred to as a“moving average.” Empirical testing or calculation may be used todetermine the number of samples to be used for the valueCCU_1YSigned_A_MA. The moving average values of the associated filteredacceleration signal CCU_1Y from the second crash acceleration sensor 34are computed using “signed” values of the acceleration signal.Specifically, the direction of acceleration sensed by the second crashacceleration sensor 34 is reflected by providing a sign, i.e., plus orminus, for each value of the acceleration signal CCU_1Y. Those signs areconsidered in determining the crash metric value CCU_1YSigned_A_MA.

The value CCU_1X_Long_A_MA is a moving average of acceleration as sensedby the first crash acceleration sensor 32. This value is determined bycalculating moving average values of the associated filteredacceleration signal CCU_1X from the first crash acceleration sensor 32.As previously explained, a moving average is the sum of the lastpredetermined number of samples of the filtered acceleration signaldivided by the number of samples. The average is updated by removing theoldest sample, replacing it with the latest sample, and then determiningthe new average. As the average value changes or “moves” over time, itis referred to as a “moving average.” Empirical testing or calculationmay be used to determine the number of samples to be used for the valueCCU_1X_Long_A_MA.

The determination and comparison function 90 of the controller 70compares the value CCU_1YSigned_A_MA against a threshold. The thresholdmay be variable or may be fixed. Specifically, the determination andcomparison function 90 compares the CCU_1YSigned_A_MA value as afunction of the CCU_1X_Long_A_MA value against a varying threshold 94. Agraphical representation of the variation of the threshold 94, inaccordance with one example embodiment of the invention, is included inFIG. 3. As can be seen, after an initial high plateau followed by alarge step or drop, the threshold 94 generally decreases with increasingCCU_1X_Long_A_MA values and ultimately becomes constant. Empiricaltesting or calculation may be used to determine the variation in thethreshold 94 as a function of the CCU_1X_Long_A_MA value to produce thedesired control effect for deployment of the occupant restraintdevice(s). The occurrence of the CCU_1YSigned_A_MA value exceeding thethird threshold 94, as determined by determination and comparisonfunction 90, is time latched by a latch function (not shown) ofcontroller 70, which provides a digital HIGH signal to an OR function 96of the controller for a predetermined time period.

The filtered crash acceleration signals CCU_1Y and CCU_1X from the A/Dconverter functions 88 and 74, respectively, are also provided toanother determination and comparison function 100 of the controller 70.The determination and comparison function 100 determines the crashmetric value CCU_1YSigned_A_MA from the filtered crash accelerationsignal CCU_1Y and determines the crash metric value CCU_1X_Long_A_MAfrom the filtered crash acceleration signal CCU_1X. Alternatively, thecrash metric values CCU_1YSigned_A_MA and CCU_1X_Long_A_MA may beprovided to the determination and comparison function 100 by thedetermination and comparison function 90.

The determination and comparison function 100 compares the valueCCU_1YSigned_A_MA against different thresholds. The different thresholdsmay be variable or may be fixed. Specifically, the determination andcomparison function 100 compares the CCU_1YSigned_A_MA value as afunction of the CCU_1X_Long_A_MA value-against a varying threshold 102and a varying threshold 104. Graphical representations of the variationsof the thresholds 102 and 104, in accordance with one example embodimentof the invention, are depicted in FIG. 3. As can be seen, the thresholds102 and 104 generally increase with increasing CCU_1X_Long_A_MA values.Empirical testing or calculation may be used to determine the variationsin the thresholds 102 and 104 as a function of the CCU_1X_Long_A_MAvalue to achieve a desired control function for deployment of theoccupant restraint device(s).

If the CCU_1YSigned_A_MA value remains less than the threshold 104 andgreater than the threshold 102 and also moves progressively throughthree zones (marked 1, 2 and 3 in FIG. 3) delineated between thethresholds 102 and 104, as determined by determination and comparisonfunction 100, this occurrence is time latched by a latch function (notshown) of controller 70. This provides a digital HIGH signal to ORfunction 96 of the controller for a predetermined time period. When ORfunction 96 receives a digital HIGH either from the determination andcomparison function 90 or from the determination and comparison function100, via their respective time latch functions, the OR function is ON orHIGH and provides a digital HIGH signal to one input of an AND function106.

The filtered crash acceleration signals CCU_1Y and CCU_1X from the A/Dconverter functions 88 and 74, respectively, are provided to a furtherdetermination and comparison function 108 of the controller 70. Thedetermination and comparison function 108 determines a crash metricvalue CCU_1YUnsigned_A_MA from the filtered crash acceleration signalCCU_1Y and determines a crash metric value CCU_1X_Short_A_MA from thefiltered crash acceleration signal CCU_1×.

The crash metric value CCU_1YUnsigned_A_MA is determined in the samemanner as the value CCU_1YSigned_A_MA, except that the direction ofacceleration sensed by the second crash acceleration sensor 34 isignored for each value of the acceleration signal CCU_1Y. Thus, unsignedvalues of the acceleration signal CCU_1Y (i.e., their absolute values)are used in determining the crash metric value CCU_1YUnsigned_A_MA.Similarly, the crash metric value CCU_1X_Short_A_MA is determined in thesame manner as the crash metric value CCU_1X_Long_A_MA, except that thepredetermined number of samples of the filtered acceleration signal usedto determine CCU_1X_Short_A_MA is smaller than the predetermined numberof samples used to determine the value CCU_1X_Long_A_MA. Empiricaltesting or calculation may be used to determine the number of samples tobe used for the value CCU_1YUnsigned_A_MA and for the valueCCU_1X_Short_A_MA to provide the desired control of the occupantrestraint device(s).

The determination and comparison function 108 of the controller 70compares the value CCU_1YUnsigned_A_MA against a threshold. Thethreshold may be variable or may be fixed. Specifically, thedetermination and comparison function 108 compares theCCU_1YUnsigned_A_MA value as a function of the CCU_1X_Short_A_MA valueagainst a varying threshold 110. A graphical representation of thevariation of the threshold 110, in accordance with one exampleembodiment of the invention, is depicted in FIG. 3. As can be seen,after an initial high plateau followed by a large step or drop, thethreshold 110 remains relatively flat, although it includes severalsmall value steps, with increasing CCU_1X_Short_A_MA values. Empiricaltesting or calculation may be used to determine the variation in thethreshold 110 as a function of the CCU_1X_Short_A_MA value to achievethe desired deployment control. The occurrence of theCCU_1YUnsigned_A_MA value exceeding the threshold 110, as determined bydetermination and comparison function 108, is time latched by a latchfunction (not shown) of controller 70. This provides a digital HIGHsignal to AND function 106 of the controller for a predetermined timeperiod.

When the AND function 106; receives digital HIGH signals from both theOR function 96 and the determination and comparison function 108, viaits associated time latch function, the AND function 106 is ON or HIGHand provides a digital HIGH signal to one input of AND function 84 andto determination and comparison function 76. In response to receiving adigital HIGH signal from AND function 106, determination and comparisonfunction 76 switches thresholds used in its comparison function.Specifically, rather than comparing the VEL_REL_1X value as a functionof the DISPL_REL_1X value against a first varying discriminationthreshold 78 and a second varying discrimination threshold 80, thedetermination and comparison function 76 compares the VEL_REL_1X valueagainst a single switched discrimination threshold 112. As shown by wayof the example embodiment control arrangement in FIG. 3, switchedthreshold 112 increases slightly with increasing displacementDISPL_REL_1X in the same general manner as the first and second varyingthresholds 78 and 80, but remains at lower values than the first and thesecond varying thresholds 78 and 80. Although a single switchedthreshold 112 is shown in FIG. 3, if multiple thresholds are desired tocontrol different occupant restraint devices or other safety devices,additional switched thresholds may be employed in the control process ofFIGS. 3 and 4.

The occurrence of the VEL_REL_1X value exceeding the switched threshold112, as determined by determination and comparison function 76, is timelatched by a latch function (not shown) of controller 70, which providesa digital HIGH signal to AND function 84 of the controller 70 for apredetermined time period. When AND function 84 receives a digital HIGHsignal from AND function 106 and from the determination and comparisonfunction 76, based on a comparison of the VEL_REL_1X value as a functionof the DISPL_REL_1X value against the switched threshold 112, the ANDfunction 84 is ON or HIGH and provides a digital HIGH signal to oneinput of AND function 114 (FIG. 4).

Also in accordance with the example embodiment control process of FIGS.3 and 4, the side satellite crash acceleration sensor 36 provides anacceleration signal RAS_1BY having a characteristic (e.g., frequency andamplitude) indicative of the vehicle's acceleration in a directionsubstantially parallel to the Y-axis of the vehicle 12. The accelerationsignal RAS_1BY is provided to an LPF function 116 of the controller 70.The LPF function 116 filters the acceleration signal RAS_1BY toeliminate extraneous signal components, such as frequencies resultingfrom extraneous vehicle operating events and/or from road noise. Thesignal components removed through filtering are not useful indiscriminating whether a vehicle crash event is occurring and whether avehicle crash event is occurring for which deployment of a driver sideactuatable occupant restraint device, such as the first frontalinflatable occupant restraint device 16, is desired. Empirical testingor calculation may be used to determine the signal components useful fordiscrimination of a vehicle crash condition in a vehicle of interestand/or determining whether a vehicle crash event is occurring for whichdeployment of a driver side actuatable occupant restraint device isdesired. Signal components indicative of a vehicle crash conditionand/or useful in determining whether a vehicle crash event is occurringfor which deployment of a driver side actuatable occupant restraintdevice is desired are output for further processing.

Further in accordance with the example embodiment control process ofFIGS. 3 and 4, the side satellite crash acceleration sensor 38 providesan acceleration signal RAS_2BY having a characteristic (e.g., frequencyand amplitude) indicative of the vehicle's acceleration in a directionsubstantially parallel to the Y-axis of the vehicle 12. The accelerationsignal RAS_2BY is provided to an LPF function 118 of the controller 70.The LPF function 118 filters the acceleration signal RAS_2BY toeliminate extraneous signal components, such as frequencies resultingfrom extraneous vehicle operating events and/or from road noise. Thesignal components removed through filtering are not useful indiscriminating whether a vehicle crash event is occurring and whether avehicle crash event is occurring for which deployment of a driver sideactuatable occupant restraint device, such as the first frontalinflatable occupant restraint device 16, is desired. Empirical testingor calculation may be used to determine the signal components useful fordiscrimination of a vehicle crash condition in a vehicle of interestand/or determining whether a vehicle crash event is occurring for whichdeployment of a driver side actuatable occupant restraint device isdesired. Signal components indicative of a vehicle crash conditionand/or useful in determining whether a vehicle crash event is occurringfor which deployment of a driver side actuatable occupant restraintdevice is desired are output for further processing.

The filtered output signals from the LPF functions 116 and 118 areprovided to A/D converter functions 120 and 122, respectively, of thecontroller 70. The A/D converter functions 120 and 122 convert thefiltered crash acceleration signals into digital signals. The outputs ofthe A/D converter functions 120 and 122 may be filtered with otherfilter functions (not shown) having filter values determined for thepurpose of eliminating small drifts and offsets associated with the A/Dconversion. These other filter functions may be digitally implementedwithin the controller 70. The filtered crash acceleration signalsRAS_1BY and RAS_2BY are provided to two determination functions 124 and126. Determination function 124 of the controller 70 determines atransverse crash metric value ∥A∥_MA_A_RAS_1BY from the filtered crashacceleration signal RAS_1BY. Determination function 126 of thecontroller 70 determines a transverse crash metric value∥A∥_MA_A_RAS_2BY from the filtered crash acceleration signal RAS_2BY.

The values ∥A∥_MA_A_RAS_1BY and ∥A∥_MA_A_RAS_2BY are moving averages ofthe absolute values of acceleration as sensed by the side satellitecrash acceleration sensors 36 and 38, respectively. These values aredetermined by calculating moving averages of the absolute values of theassociated filtered acceleration signals RAS_1BY and RAS_2BY from theside satellite crash acceleration sensors 36 and 38, respectively. Aspreviously explained, a moving average is the sum of the lastpredetermined number of samples of the filtered acceleration signaldivided by the number of samples. The average is updated by removing theoldest sample, replacing it with the latest sample, and then determiningthe new average. As the average value changes or “moves” over time, itis referred to as a “moving average.” Empirical testing or calculationmay be used to determine the number of samples to be used for each ofthe values ∥A∥_MA_A_RAS_1BY and ∥A∥_MA_A_RAS_2BY.

The values ∥A∥_MA_A_RAS_1BY and ∥A∥_MA_A_RAS_2BY are provided to asumming function 128 of the controller 70. The summing function 128 addsthe values ∥A∥_MA_A_RAS_1BY and ∥A∥_MA_A_RAS_2BY to determine atransverse crash metric value that is a sum of the moving averages ofthe absolute values of acceleration as sensed by the side satellitecrash acceleration sensors 36 and 38. A comparison function of thecontroller 70 compares the sum of the values ∥A∥_MA_A_RAS_1BY and∥A∥_MA_A_RAS_2BY against a threshold, which may be fixed or may bevariable. Specifically, a comparison function 130 compares the sum ofthe values ∥A∥_MA_A_RAS_1BY and ∥A∥MA_A_RAS_2BY against a safingthreshold 132. Empirical testing or calculation may be used to determinethe value of the safing threshold 132 for a vehicle of interest.

The occurrence of the sum of the values ∥A∥_MA_A_RAS_1BY and∥A∥_MA_A_RAS_2BY exceeding the safing threshold 132, as determined bycomparison function 130, is time latched by latch function (not shown)of controller 70, which provides a digital HIGH signal to AND function114 of the controller for a predetermined time period. When the ANDfunction 114 is ON or HIGH, as a result of receiving digital HIGHsignals from both the comparison function 130, via its associated timelatch function, and either the AND function 84 or, as previouslydescribed, the determination and comparison function 76, the ANDfunction 114 provides a digital HIGH signal to a crash conditiondetermination and deployment control function 134, which determines thata crash condition of the vehicle 12 is occurring. The crash conditiondetermination and deployment control function 134 of the controller 70also determines whether a vehicle crash event is occurring for whichdeployment or actuation of an actuatable occupant restraint device, suchas the first frontal inflatable occupant restraint device 16 or thedriver side seat belt pretensioner 28, or any other vehicle safetydevice is desired. If deployment is desired, the controller 70 outputs adeployment signal to the actuatable occupant restraint device, such asthe first frontal inflatable occupant restraint device 16 and/or thedriver side seat belt pretensioner 28, which deploys in response to thedeployment signal. The deployment or actuation decision may be basedsolely on the determination that a vehicle crash condition is occurringor other inputs may be considered in making the deployment or actuationdecision.

A second embodiment of the control process and logic used by thecontroller 70 to control the actuatable occupant restraint system 14 isshown in FIG. 5. The process and logic of FIG. 5 is specificallydirected to controlling an actuatable occupant restraint device on thedriver side 18 of the vehicle 12, such as the first frontal inflatableoccupant restraint device 16. Nonetheless, FIG. 5 is representative of aprocess and logic that may be used to control the second frontalinflatable occupant restraint device 20 on the passenger side 22 of thevehicle 12 and any other actuatable occupant restraint device that helpsto protect a vehicle occupant in response to a crash condition of thevehicle 12. The control process and logic of FIG. 5 may also be used tocontrol any actuatable safety device of the vehicle 12, such as vehicledoor locks, a suspension control system, a deployable roll bar and/or anexternal air bag or other inflatable device external or internal to thevehicle.

In the control process of FIG. 5, the first crash acceleration sensor 32provides an acceleration signal CCU_1X to the controller 70, and thesecond crash acceleration sensor 34 provides an acceleration signalCCU_1Y to the controller, just as in the control process of FIGS. 3 and4. The controller 70 processes the signals CCU_1X and CCU_1Y in the samemanner and with the same functions as in the control process of FIGS. 3and 4 through and including the AND function 106 of the controller. Thecontrol process of FIG. 5 differs, however, from the control process ofFIGS. 3 and 4 in that acceleration signals RAS_1BX and RAS_2BX from theside satellite crash acceleration sensors 40 and 46, respectively, areused in the control process of FIG. 5, as explained below. Because thecontrol process and logic of FIG. 5 is identical in many respects to thecontrol process and logic of FIGS. 3 and 4, FIG. 5 illustrates only thepart of the second embodiment of the control process and logic used bythe controller 70 that differs from the control process of FIGS. 3 and4. The part of the control process shown in FIG. 5 interfaces with thecontrol process shown in FIGS. 3 and 4 at points B and C of FIG. 3, justafter AND function 106 and before AND function 84.

In accordance with the example embodiment control process of FIG. 5, theside satellite crash acceleration sensor 40 provides an accelerationsignal RAS_1BX having a characteristic (e.g., frequency and amplitude)indicative of the vehicle's acceleration in a direction substantiallyparallel to the X-axis of the vehicle 12. The acceleration signalRAS_1BX is provided to an LPF function 140 of the controller 70. The LPFfunction 140 filters the acceleration signal RAS_1BX to eliminateextraneous signal components, such as frequencies resulting fromextraneous vehicle operating events and/or from road noise. The signalcomponents removed through filtering are not useful in discriminatingwhether a vehicle crash event is occurring and whether a vehicle crashevent is occurring for which deployment of a driver side actuatableoccupant restraint device, such as the first frontal inflatable occupantrestraint device 16, is desired. Empirical testing or calculation may beused to determine the signal components useful for discrimination of avehicle crash condition in a vehicle of interest and/or determiningwhether a vehicle crash event is occurring for which deployment of adriver side actuatable occupant restraint device is desired. Signalcomponents indicative of a vehicle crash condition and/or useful indetermining whether a vehicle crash event is occurring for whichdeployment of a driver side actuatable occupant restraint device isdesired are output for further processing.

Also in accordance with the example embodiment control process of FIG.5, the side satellite crash acceleration sensor 46 provides anacceleration signal RAS_2BX having a characteristic (e.g., frequency andamplitude) indicative of the vehicle's acceleration in a directionsubstantially parallel to the X-axis of the vehicle 12. The accelerationsignal RAS_2BX is provided to an LPF function 142 of the controller 70.The LPF function 142 filters the acceleration signal RAS_2BX toeliminate extraneous signal components, such as frequencies resultingfrom extraneous vehicle operating events and/or from road noise. Thesignal components removed through filtering are not useful indiscriminating whether a vehicle crash event is occurring and whether avehicle crash event is occurring for which deployment of a driver sideactuatable occupant restraint device, such as the first frontalinflatable occupant restraint device 16, is desired. Empirical testingor calculation may be used to determine the signal components useful fordiscrimination of a vehicle crash condition in a vehicle of interestand/or determining whether a vehicle crash event is occurring for whichdeployment of a driver side actuatable occupant restraint device isdesired. Signal components indicative of a vehicle crash conditionand/or useful in determining whether a vehicle crash event is occurringfor which deployment of a driver side actuatable occupant restraintdevice is desired are output for further processing.

The filtered output signals from the LPF functions 140 and 142 areprovided to A/D converter functions 144 and 146, respectively, of thecontroller 70. The A/D converter functions 144 and 146 convert thefiltered crash acceleration signals into digital signals. The outputs ofthe A/D converter functions 144 and 146 may be filtered with otherfilter functions (not shown) having filter values determined for thepurpose of eliminating small drifts and offsets associated with the A/Dconversion. These other filter functions may be digitally implementedwithin the controller 70.

The filtered crash acceleration signals RAS_1BX and RAS_2BX, as well asthe filtered crash acceleration signal CCU_1Y from the A/D converterfunction 88, are provided to two determination and discriminationfunctions 148 and 150. Determination and comparison function 148 of thecontroller 70 determines a crash metric value CCU_1Y_NFSigned_A_MA fromthe filtered crash acceleration signal CCU_1Y and determines a crashmetric value LRBX_SUM_NF from the filtered crash acceleration signalsRAS_1BX and RAS_2BX. Determination and comparison function 150 of thecontroller 70 determines a crash metric value CCU_1Y_MUSigned_A_MA fromthe filtered crash acceleration signal CCU_1Y and determines a crashmetric value LRBX_SUM_MU from the filtered crash acceleration signalsRAS_1BX and RAS_2BX.

The crash metric values CCU_1Y_NFSigned_A_MA and CCU_1Y_MUSigned_A_MAare determined in the same manner as the crash metric valueCCU_1YSigned_A_MA, except for the predetermined number of samples of thefiltered acceleration signal CCU_1Y used. Specifically, thepredetermined numbers of samples used to determine the valueCCU_1Y_NFSigned_A_MA and the value CCU_1Y_MUSigned_A_MA may be differentfrom the number used to determine the value CCU_1YSigned_A_MA. Inaddition, the predetermined number of samples of the filteredacceleration signal CCU_1Y used to determine the valueCCU_1Y_NFSigned_A_MA may be different from the number used to determinethe value CCU_1Y_MUSigned_A_MA. Empirical testing or calculation may beused to determine the number of samples to be used for the valueCCU_1Y_NFSigned_A_MA and for the value CCU_1Y_MUSigned_A_MA.

The values LRBX_SUM_NF and LRBX_SUM_MU are the sums of moving averagesof acceleration as sensed by the side satellite crash accelerationsensors 40 and 46. These values are determined by calculating movingaverage values of the associated filtered acceleration signals RAS_1BXand RAS_2BX from the side satellite crash acceleration sensors 40 and 46and adding together the determined moving average values. As previouslyexplained, a moving average is the sum of the last predetermined numberof samples of the filtered acceleration signal divided by the number ofsamples. The average is updated by removing the oldest sample, replacingit with the latest sample, and then determining the new average. As theaverage value changes or “moves” over time, it is referred to as a“moving average.” Empirical testing or calculation may be used todetermine the number of samples to be used for the values LRBX_SUM_NFand LRBX_SUM_MU. The predetermined number of samples of the filteredacceleration filtered acceleration signals RAS_1BX and RAS_2BX used todetermine the value LRBX_SUM_NF may be different from the number used todetermine the value LRBX_SUM_MU.

The determination and comparison function 148 of the controller 70compares the value CCU_1Y_NFSigned_A_MA against a threshold. Thethreshold may be variable or may be fixed. Specifically, thedetermination and comparison function 148 compares theCCU_1Y_NFSigned_A_MA value as a function of the LRBX_SUM_NF valueagainst a varying threshold 152. A graphical representation of thevariation of the threshold 152, in accordance with one exampleembodiment of the present invention, is depicted in FIG. 5. As can beseen, after an initial high plateau followed by a large step or drop,the threshold 152 remains relatively flat, although it includes severalsmall value steps, with increasing LRBX_SUM_NF values. Empirical testingor calculation may be used to determine the variation in the threshold152 as a function of the LRBX_SUM_NF value to provide the desiredcontrol of the restraint device(s). The occurrence of theCCU_1Y_NFSigned_A_MA value exceeding the threshold 152, as determined bydetermination and comparison function 148, is time latched by a latchfunction (not shown) of controller 70. This provides a digital HIGHsignal to AND function 156 of the controller for a predetermined timeperiod.

The determination and comparison function 150 of the controller 70compares the value CCU_1Y_MUSigned_A_MA against a threshold. Thethreshold may be variable or may be fixed. Specifically, thedetermination and comparison function 150 compares theCCU_1Y_MUSigned_A_MA value as a function of the LRBX_SUM_MU valueagainst a threshold 154. A graphical representation of the variation ofthe threshold 154, in accordance with one example embodiment of thepresent invention, is depicted in FIG. 5. As can be seen, after aninitial high plateau followed by a large step or drop, the threshold 154generally decreases with increasing LRBX_SUM_MU values and ultimatelybecomes constant. Empirical testing or calculation may be used todetermine the variation in the threshold 154 as a function of theLRBX_SUM_MU value to provide the desired control of the restraintdevice(s). The occurrence of the CCU_1Y_MUSigned_A_MA value exceedingthe threshold 154, as determined by determination and comparisonfunction 150, is time latched by a latch function (not shown) ofcontroller 70. This provides a digital HIGH signal to AND function 156of the controller for a predetermined time period.

When the AND function 156 receives digital HIGH signals from both thedetermination and comparison function 148 and the determination andcomparison function 150, via their associated time latch functions, theAND function 156 is ON or HIGH and provides a digital HIGH signal to ORfunction 158. When OR function 158 receives a digital HIGH from eitherthe AND function 106 (FIG. 3) or the AND function 156, the OR functionis ON or HIGH and provides a digital HIGH signal to AND function 84(FIG. 3) and to determination and comparison function 76. In response toreceiving a digital HIGH signal from OR function 158, determination andcomparison function 76 switches thresholds. Specifically, rather thancomparing the VEL_REL_1X value as a function of the DISPL_REL_1X valueagainst a first varying discrimination threshold 78 and a second varyingdiscrimination threshold 80, the determination and comparison function76 compares the VEL_REL_1X value against a single switcheddiscrimination threshold 112. As shown by way of the example embodimentcontrol arrangement in FIG. 3, switched threshold 112 increases slightlywith increasing displacement DISPL_REL_1X in the same general manner asthe first and second varying thresholds 78 and 80, but remains at lowervalues than the first and second varying thresholds 78 and 80. Althougha single switched threshold 112 is shown in FIG. 3, if multiplethresholds are desired to control different occupant restraint devicesor other safety devices, additional thresholds may be employed in thecontrol process of FIG. 5.

The occurrence of the VEL_REL_1X value exceeding the switched threshold112, as determined by determination and comparison function 76, is timelatched by a latch function (not shown) of controller 70, which providesa digital HIGH signal to the AND function 84 of the controller 70 for apredetermined time period. When AND function 84 receives a digital HIGHsignal from OR function 158 and from the determination and comparisonfunction 76, based on a comparison of the VEL_REL_1X value as a functionof the DISPL_REL_1X value against the switched threshold 112, the ANDfunction 84 is ON or HIGH and provides a digital HIGH signal to ANDfunction 114 (FIG. 4). From this point on, the control process of FIG. 5continues in the same manner and with the same functions as in thecontrol process of FIGS. 3 and 4 through and including the crashcondition determination and deployment control function 134, whichdetermines that a crash condition of the vehicle 12 is occurring.

The crash condition determination and deployment control function 134 ofthe controller 70 also determines whether a vehicle crash event isoccurring for which deployment or actuation of an actuatable occupantrestraint device, such as the first frontal inflatable occupantrestraint device 16 or the driver side seat belt pretensioner 28, or anyother vehicle safety device is desired. If deployment is desired, thecontroller 70 outputs a deployment signal to the actuatable occupantrestraint device, such as the first frontal inflatable occupantrestraint device 16 and/or the driver side seat belt pretensioner 28,which deploy in response to the deployment signal. The deployment oractuation decision may be based solely on the determination that avehicle crash condition is occurring or other inputs may be consideredin making the deployment or actuation decision.

From the above description of the invention, those skilled in the artwill perceive improvements, changes and modifications. Suchimprovements, changes, and/or modifications within the skill of the artare intended to be covered by the appended claims.

1. A method for determining a crash condition of a vehicle comprisingthe steps of: sensing crash acceleration in a first directionsubstantially parallel to a front-to-rear axis of the vehicle andproviding a first acceleration signal indicative thereof; sensing crashacceleration in a second direction substantially parallel to aside-to-side axis of the vehicle and near opposite sides of the vehicleand providing second acceleration signals indicative thereof;determining a transverse crash value functionally related to the secondacceleration signals; comparing the determined transverse crash valueagainst a safing threshold; and determining a crash condition of thevehicle in response to (a) the comparison and (b) the first accelerationsignal wherein said step of determining a transverse crash valuefunctionally related to the second acceleration signals includes thestep of determining a sum of moving averages of absolute values ofacceleration in the second direction based on the second accelerationsignals.
 2. The method of claim 1 further comprising the step ofproviding an actuation signal for actuating an actuatable safety deviceof the vehicle in response to determining a crash condition of thevehicle.
 3. The method of claim 1 wherein said step of determining atransverse crash value functionally related to the second accelerationsignals includes the steps of: determining moving averages of absolutevalues of acceleration in the second direction based on the secondacceleration signals, and determining the transverse crash value basedon the determined moving averages of absolute values of acceleration inthe second direction.
 4. The method of claim 3 wherein said step ofdetermining the transverse crash value based on the determined movingaverages of absolute values of acceleration in the second directionincludes the step of determining the transverse crash value based on thedetermined sum of the moving averages of absolute values of accelerationin the second direction.
 5. The method of claim 1 further comprising thesteps of: determining crash velocity in said first direction from thefirst acceleration signal; determining crash displacement in said firstdirection from the first acceleration signal; and comparing thedetermined crash velocity as a function of the determined crashdisplacement against one of a discrimination threshold and a switcheddiscrimination threshold; and wherein said step of determining a crashcondition of the vehicle comprises determining a crash condition of thevehicle in response to both the determined crash velocity as a functionof crash displacement exceeding one of the discrimination threshold andthe switched discrimination threshold and the transverse crash valueexceeding the safing threshold.
 6. An apparatus for determining a crashcondition of a vehicle, said apparatus comprising: a first accelerometerfor sensing crash acceleration in a first direction substantiallyparallel to a front-to-rear axis of the vehicle and providing a firstacceleration signal indicative thereof; second accelerometers forsensing crash acceleration in a second direction substantially parallelto a side-to-side axis of the vehicle and near opposite sides of thevehicle and providing second acceleration signals indicative thereof;and a controller determining a transverse crash value functionallyrelated to the second acceleration signals and comparing the transversecrash value against a safing threshold, the controller also determininga crash condition of the vehicle in response to (a) the comparison and(b) the first acceleration signal wherein the controller determines thetransverse crash value as a sum of moving averages of absolute values ofacceleration in the second direction based on the second accelerationsignals.
 7. The apparatus of claim 6 wherein the controller alsoprovides an actuation signal for actuating an actuatable safety deviceof the vehicle in response to determining a crash condition of thevehicle.
 8. The apparatus of claim 6 wherein the controller determinesthe transverse crash value from moving averages of absolute values ofacceleration in the second direction based on the second accelerationsignals.
 9. The apparatus of claim 6 wherein the controller furtherdetermines a crash velocity and a crash displacement from the firstacceleration signal and compares the determined crash velocity as afunction of the determined crash displacement against one of adiscrimination threshold and a switched discrimination threshold, thecontroller determining a crash condition of the vehicle in response toboth (a) the determined crash velocity as a function of the determinedcrash displacement exceeding one of the discrimination threshold and theswitched discrimination threshold and (b) the transverse crash valueexceeding the safing threshold.
 10. The apparatus of claim 9 wherein atleast one of the discrimination and transverse thresholds is a variablethreshold.
 11. The apparatus of claim 9 wherein at least one of thediscrimination and transverse thresholds is a fixed threshold.
 12. Theapparatus of claim 6 wherein the first accelerometer is located at asubstantially central vehicle location.